The RBT service is a multimedia service, where a mobile telephone subscriber and a fixed telephone subscriber (including wired fixed telephone subscriber and wireless fixed telephone subscriber) customize a special ring back tone which is played to the calling party in place of a traditional ring back tone. In the networks of different operators, the RBT service may be identified by different trade names.
The system and method for implementing the Multimedia Ring Back Tone (MRBT) service in the prior art implement the RBT function of the 3G Circuit Switched (CS) domain and the RBT function of the 3G Packet Switched (PS) domain, including the RBT function of the IP Multimedia Subsystem (IMS) domain.
However, in the research process, the inventor finds that the prior art enables only the calling terminal in the PS core network to receive the signal tone from a called party in the traditional CS domain, without enabling the calling terminal in the CS domain to receive an MRBT from a called party in the PS core network. This function unavailable from the prior art involves the following technical problems: When a CS user makes a call (video call) to an IMS user, the home Mobile Switching Center (MSC) server of the calling terminal (namely, the originating MSC server) is unable to query whether the called party has subscribed to the MRBT service in a different domain. Moreover, after an Alerting message is received from the called party, it is uncertain whether the calling party needs to be put through, and it is thus impossible to play any IMS video RBT to the CS user.